Reorganize syscall entry and leave handling.

Extend struct sysvec with three new elements:
sv_fetch_syscall_args - the method to fetch syscall arguments from
  usermode into struct syscall_args. The structure is machine-depended
  (this might be reconsidered after all architectures are converted).
sv_set_syscall_retval - the method to set a return value for usermode
  from the syscall. It is a generalization of
  cpu_set_syscall_retval(9) to allow ABIs to override the way to set a
  return value.
sv_syscallnames - the table of syscall names.

Use sv_set_syscall_retval in kern_sigsuspend() instead of hardcoding
the call to cpu_set_syscall_retval().

The new functions syscallenter(9) and syscallret(9) are provided that
use sv_*syscall* pointers and contain the common repeated code from
the syscall() implementations for the architecture-specific syscall
trap handlers.

Syscallenter() fetches arguments, calls syscall implementation from
ABI sysent table, and set up return frame. The end of syscall
bookkeeping is done by syscallret().

Take advantage of single place for MI syscall handling code and
implement ptrace_lwpinfo pl_flags PL_FLAG_SCE, PL_FLAG_SCX and
PL_FLAG_EXEC. The SCE and SCX flags notify the debugger that the
thread is stopped at syscall entry or return point respectively.  The
EXEC flag augments SCX and notifies debugger that the process address
space was changed by one of exec(2)-family syscalls.

The i386, amd64, sparc64, sun4v, powerpc and ia64 syscall()s are
changed to use syscallenter()/syscallret(). MIPS and arm are not
converted and use the mostly unchanged syscall() implementation.

Reviewed by:	jhb, marcel, marius, nwhitehorn, stas
Tested by:	marcel (ia64), marius (sparc64), nwhitehorn (powerpc),
	stas (mips)
MFC after:	1 month

5 files changed, 78 insertions, 159 deletions

diff --git a/sys/i386/i386/elf_machdep.c b/sys/i386/i386/elf_machdep.c
index 408d6ad..df3f48f 100644
--- a/sys/i386/i386/elf_machdep.c
+++ b/sys/i386/i386/elf_machdep.c
@@ -32,6 +32,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/exec.h>
 #include <sys/imgact.h>
 #include <sys/linker.h>
+#include <sys/proc.h>
 #include <sys/sysent.h>
 #include <sys/imgact_elf.h>
 #include <sys/syscall.h>
@@ -73,7 +74,10 @@ struct sysentvec elf32_freebsd_sysvec = {
 	.sv_setregs	= exec_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_FREEBSD | SV_IA32 | SV_ILP32
+	.sv_flags	= SV_ABI_FREEBSD | SV_IA32 | SV_ILP32,
+	.sv_set_syscall_retval = cpu_set_syscall_retval,
+	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
+	.sv_syscallnames = syscallnames,
 };
 
 static Elf32_Brandinfo freebsd_brand_info = {
diff --git a/sys/i386/i386/trap.c b/sys/i386/i386/trap.c
index a11daa6..644bb47 100644
--- a/sys/i386/i386/trap.c
+++ b/sys/i386/i386/trap.c
@@ -184,8 +184,6 @@ static int prot_fault_translation = 0;
 SYSCTL_INT(_machdep, OID_AUTO, prot_fault_translation, CTLFLAG_RW,
 	&prot_fault_translation, 0, "Select signal to deliver on protection fault");
 
-extern char *syscallnames[];
-
 /*
  * Exception, fault, and trap interface to the FreeBSD kernel.
  * This common code is called from assembly language IDT gate entry
@@ -973,16 +971,8 @@ dblfault_handler()
 	panic("double fault");
 }
 
-struct syscall_args {
-	u_int code;
-	struct sysent *callp;
-	int args[8];
-	register_t *argp;
-	int narg;
-};
-
-static int
-fetch_syscall_args(struct thread *td, struct syscall_args *sa)
+int
+cpu_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 {
 	struct proc *p;
 	struct trapframe *frame;
@@ -995,27 +985,22 @@ fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 	params = (caddr_t)frame->tf_esp + sizeof(int);
 	sa->code = frame->tf_eax;
 
-	if (p->p_sysent->sv_prepsyscall) {
-		(*p->p_sysent->sv_prepsyscall)(frame, sa->args, &sa->code,
-		    &params);
-	} else {
+	/*
+	 * Need to check if this is a 32 bit or 64 bit syscall.
+	 */
+	if (sa->code == SYS_syscall) {
 		/*
-		 * Need to check if this is a 32 bit or 64 bit syscall.
+		 * Code is first argument, followed by actual args.
 		 */
-		if (sa->code == SYS_syscall) {
-			/*
-			 * Code is first argument, followed by actual args.
-			 */
-			sa->code = fuword(params);
-			params += sizeof(int);
-		} else if (sa->code == SYS___syscall) {
-			/*
-			 * Like syscall, but code is a quad, so as to maintain
-			 * quad alignment for the rest of the arguments.
-			 */
-			sa->code = fuword(params);
-			params += sizeof(quad_t);
-		}
+		sa->code = fuword(params);
+		params += sizeof(int);
+	} else if (sa->code == SYS___syscall) {
+		/*
+		 * Like syscall, but code is a quad, so as to maintain
+		 * quad alignment for the rest of the arguments.
+		 */
+		sa->code = fuword(params);
+		params += sizeof(quad_t);
 	}
 
  	if (p->p_sysent->sv_mask)
@@ -1031,11 +1016,12 @@ fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 		    (u_int)(sa->narg * sizeof(int)));
 	else
 		error = 0;
+
+	if (error == 0) {
+		td->td_retval[0] = 0;
+		td->td_retval[1] = frame->tf_edx;
+	}
 		
-#ifdef KTRACE
-	if (KTRPOINT(td, KTR_SYSCALL))
-		ktrsyscall(sa->code, sa->narg, sa->args);
-#endif
 	return (error);
 }
 
@@ -1048,87 +1034,23 @@ void
 syscall(struct trapframe *frame)
 {
 	struct thread *td;
-	struct proc *p;
 	struct syscall_args sa;
 	register_t orig_tf_eflags;
 	int error;
 	ksiginfo_t ksi;
 
-	PCPU_INC(cnt.v_syscall);
-	td = curthread;
-	p = td->td_proc;
-	td->td_syscalls++;
-
 #ifdef DIAGNOSTIC
 	if (ISPL(frame->tf_cs) != SEL_UPL) {
 		panic("syscall");
 		/* NOT REACHED */
 	}
 #endif
-
-	td->td_pticks = 0;
-	td->td_frame = frame;
-	if (td->td_ucred != p->p_ucred) 
-		cred_update_thread(td);
 	orig_tf_eflags = frame->tf_eflags;
-	if (p->p_flag & P_TRACED) {
-		PROC_LOCK(p);
-		td->td_dbgflags &= ~TDB_USERWR;
-		PROC_UNLOCK(p);
-	}
-	error = fetch_syscall_args(td, &sa);
 
-	CTR4(KTR_SYSC, "syscall enter thread %p pid %d proc %s code %d", td,
-	    td->td_proc->p_pid, td->td_name, sa.code);
-
-	if (error == 0) {
-		td->td_retval[0] = 0;
-		td->td_retval[1] = frame->tf_edx;
-
-		STOPEVENT(p, S_SCE, sa.narg);
-		PTRACESTOP_SC(p, td, S_PT_SCE);
-		if (td->td_dbgflags & TDB_USERWR) {
-			/*
-			 * Reread syscall number and arguments if
-			 * debugger modified registers or memory.
-			 */
-			error = fetch_syscall_args(td, &sa);
-			if (error != 0)
-				goto retval;
-			td->td_retval[1] = frame->tf_edx;
-		}
-
-#ifdef KDTRACE_HOOKS
-		/*
-		 * If the systrace module has registered it's probe
-		 * callback and if there is a probe active for the
-		 * syscall 'entry', process the probe.
-		 */
-		if (systrace_probe_func != NULL && sa.callp->sy_entry != 0)
-			(*systrace_probe_func)(sa.callp->sy_entry, sa.code,
-			    sa.callp, sa.args);
-#endif
-
-		AUDIT_SYSCALL_ENTER(sa.code, td);
-		error = (*sa.callp->sy_call)(td, sa.args);
-		AUDIT_SYSCALL_EXIT(error, td);
+	td = curthread;
+	td->td_frame = frame;
 
-		/* Save the latest error return value. */
-		td->td_errno = error;
-
-#ifdef KDTRACE_HOOKS
-		/*
-		 * If the systrace module has registered it's probe
-		 * callback and if there is a probe active for the
-		 * syscall 'return', process the probe.
-		 */
-		if (systrace_probe_func != NULL && sa.callp->sy_return != 0)
-			(*systrace_probe_func)(sa.callp->sy_return, sa.code,
-			    sa.callp, sa.args);
-#endif
-	}
- retval:
-	cpu_set_syscall_retval(td, error);
+	error = syscallenter(td, &sa);
 
 	/*
 	 * Traced syscall.
@@ -1142,41 +1064,5 @@ syscall(struct trapframe *frame)
 		trapsignal(td, &ksi);
 	}
 
-	/*
-	 * Check for misbehavior.
-	 */
-	WITNESS_WARN(WARN_PANIC, NULL, "System call %s returning",
-	    (sa.code >= 0 && sa.code < SYS_MAXSYSCALL) ?
-	     syscallnames[sa.code] : "???");
-	KASSERT(td->td_critnest == 0,
-	    ("System call %s returning in a critical section",
-	    (sa.code >= 0 && sa.code < SYS_MAXSYSCALL) ?
-	     syscallnames[sa.code] : "???"));
-	KASSERT(td->td_locks == 0,
-	    ("System call %s returning with %d locks held",
-	    (sa.code >= 0 && sa.code < SYS_MAXSYSCALL) ?
-	     syscallnames[sa.code] : "???", td->td_locks));
-
-	/*
-	 * Handle reschedule and other end-of-syscall issues
-	 */
-	userret(td, frame);
-
-	CTR4(KTR_SYSC, "syscall exit thread %p pid %d proc %s code %d", td,
-	    td->td_proc->p_pid, td->td_name, sa.code);
-
-#ifdef KTRACE
-	if (KTRPOINT(td, KTR_SYSRET))
-		ktrsysret(sa.code, error, td->td_retval[0]);
-#endif
-
-	/*
-	 * This works because errno is findable through the
-	 * register set.  If we ever support an emulation where this
-	 * is not the case, this code will need to be revisited.
-	 */
-	STOPEVENT(p, S_SCX, sa.code);
-
-	PTRACESTOP_SC(p, td, S_PT_SCX);
+	syscallret(td, error, &sa);
 }
-
diff --git a/sys/i386/ibcs2/ibcs2_sysvec.c b/sys/i386/ibcs2/ibcs2_sysvec.c
index 9112ed7..71d48a3 100644
--- a/sys/i386/ibcs2/ibcs2_sysvec.c
+++ b/sys/i386/ibcs2/ibcs2_sysvec.c
@@ -86,7 +86,10 @@ struct sysentvec ibcs2_svr3_sysvec = {
 	.sv_setregs	= exec_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_UNDEF | SV_IA32 | SV_ILP32
+	.sv_flags	= SV_ABI_UNDEF | SV_IA32 | SV_ILP32,
+	.sv_set_syscall_retval = cpu_set_syscall_retval,
+	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
+	.sv_syscallnames = NULL,
 };
 
 static int
diff --git a/sys/i386/include/proc.h b/sys/i386/include/proc.h
index 86be8c8..0d92252 100644
--- a/sys/i386/include/proc.h
+++ b/sys/i386/include/proc.h
@@ -77,6 +77,14 @@ void	user_ldt_deref(struct proc_ldt *pldt);
 
 extern struct mtx dt_lock;
 
+struct syscall_args {
+	u_int code;
+	struct sysent *callp;
+	register_t args[8];
+	int narg;
+};
+#define	HAVE_SYSCALL_ARGS_DEF 1
+
 #endif	/* _KERNEL */
 
 #endif /* !_MACHINE_PROC_H_ */
diff --git a/sys/i386/linux/linux_sysvec.c b/sys/i386/linux/linux_sysvec.c
index 3f0c6f4..364cc0c 100644
--- a/sys/i386/linux/linux_sysvec.c
+++ b/sys/i386/linux/linux_sysvec.c
@@ -102,8 +102,6 @@ static int	linux_fixup(register_t **stack_base,
 		    struct image_params *iparams);
 static int	elf_linux_fixup(register_t **stack_base,
 		    struct image_params *iparams);
-static void	linux_prepsyscall(struct trapframe *tf, int *args, u_int *code,
-		    caddr_t *params);
 static void     linux_sendsig(sig_t catcher, ksiginfo_t *ksi, sigset_t *mask);
 static void	exec_linux_setregs(struct thread *td,
 		    struct image_params *imgp, u_long stack);
@@ -864,19 +862,33 @@ linux_rt_sigreturn(struct thread *td, struct linux_rt_sigreturn_args *args)
 	return (EJUSTRETURN);
 }
 
-/*
- * MPSAFE
- */
-static void
-linux_prepsyscall(struct trapframe *tf, int *args, u_int *code, caddr_t *params)
+static int
+linux_fetch_syscall_args(struct thread *td, struct syscall_args *sa)
 {
-	args[0] = tf->tf_ebx;
-	args[1] = tf->tf_ecx;
-	args[2] = tf->tf_edx;
-	args[3] = tf->tf_esi;
-	args[4] = tf->tf_edi;
-	args[5] = tf->tf_ebp;	/* Unconfirmed */
-	*params = NULL;		/* no copyin */
+	struct proc *p;
+	struct trapframe *frame;
+
+	p = td->td_proc;
+	frame = td->td_frame;
+
+	sa->code = frame->tf_eax;
+	sa->args[0] = frame->tf_ebx;
+	sa->args[1] = frame->tf_ecx;
+	sa->args[2] = frame->tf_edx;
+	sa->args[3] = frame->tf_esi;
+	sa->args[4] = frame->tf_edi;
+	sa->args[5] = frame->tf_ebp;	/* Unconfirmed */
+
+	if (sa->code >= p->p_sysent->sv_size)
+		sa->callp = &p->p_sysent->sv_table[0];
+ 	else
+ 		sa->callp = &p->p_sysent->sv_table[sa->code];
+	sa->narg = sa->callp->sy_narg;
+
+	td->td_retval[0] = 0;
+	td->td_retval[1] = frame->tf_edx;
+
+	return (0);
 }
 
 /*
@@ -972,7 +984,7 @@ struct sysentvec linux_sysvec = {
 	.sv_sendsig	= linux_sendsig,
 	.sv_sigcode	= linux_sigcode,
 	.sv_szsigcode	= &linux_szsigcode,
-	.sv_prepsyscall	= linux_prepsyscall,
+	.sv_prepsyscall	= NULL,
 	.sv_name	= "Linux a.out",
 	.sv_coredump	= NULL,
 	.sv_imgact_try	= exec_linux_imgact_try,
@@ -987,7 +999,10 @@ struct sysentvec linux_sysvec = {
 	.sv_setregs	= exec_linux_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_LINUX | SV_AOUT | SV_IA32 | SV_ILP32
+	.sv_flags	= SV_ABI_LINUX | SV_AOUT | SV_IA32 | SV_ILP32,
+	.sv_set_syscall_retval = cpu_set_syscall_retval,
+	.sv_fetch_syscall_args = linux_fetch_syscall_args,
+	.sv_syscallnames = NULL,
 };
 
 struct sysentvec elf_linux_sysvec = {
@@ -1003,7 +1018,7 @@ struct sysentvec elf_linux_sysvec = {
 	.sv_sendsig	= linux_sendsig,
 	.sv_sigcode	= linux_sigcode,
 	.sv_szsigcode	= &linux_szsigcode,
-	.sv_prepsyscall	= linux_prepsyscall,
+	.sv_prepsyscall	= NULL,
 	.sv_name	= "Linux ELF",
 	.sv_coredump	= elf32_coredump,
 	.sv_imgact_try	= exec_linux_imgact_try,
@@ -1018,7 +1033,10 @@ struct sysentvec elf_linux_sysvec = {
 	.sv_setregs	= exec_linux_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_LINUX | SV_IA32 | SV_ILP32
+	.sv_flags	= SV_ABI_LINUX | SV_IA32 | SV_ILP32,
+	.sv_set_syscall_retval = cpu_set_syscall_retval,
+	.sv_fetch_syscall_args = linux_fetch_syscall_args,
+	.sv_syscallnames = NULL,
 };
 
 static char GNU_ABI_VENDOR[] = "GNU";